Polymers, including homopolymers and copolymers, which are both biocompatible and absorbable in vivo are well known in the art. Such polymers are typically used to manufacture medical devices which are implanted in body tissue and absorb over time. Examples of such medical devices manufactured from these absorbable biocompatible polymers include suture anchor devices, sutures, staples, surgical tacks, clips, plates and screws, etc.
Absorbable, biocompatible polymers useful for manufacturing medical devices include both natural and synthetic polymers. Natural polymers include cat gut, cellulose derivatives, collagen, etc. Synthetic polymers may consist of various aliphatic polyesters, polyanhydrides, poly(orthoester)s, and the like. Natural polymers typically absorb by an enzymatic degradation process in the body, while synthetic absorbable polymers generally degrade primarily by a hydrolytic mechanism.
Synthetic absorbable polymers which are typically used to manufacture medical devices include homopolymers such as poly(glycolide), poly(tactide), poly(.epsilon.-caprolactone), poly(trimethylene carbonate) and poly(p-dioxanone) and copolymers such as poly(lactide-co-glycolide), poly(.epsilon.-caprolactone-co-glycolide), and poly(glycolide-co-trimethylene carbonate). The polymers may be statistically random copolymers, segmented copolymers, block copolymers, or graft copolymers. It is also known that both homopolymers and copolymers can be used to prepare blends.
U.S. Pat. Nos. 4,643,191, 5,080,665 describe several biocompatible, absorbable, poly(p-dioxanone-co-lactide) copolymers useful as biomedical devices.
U.S. Pat. No. 5,080,665 describes block or graft copolymers of poly(p-dioxanone-co-lactide) prepared by a process in which the p-dioxanone monomer is reacted initially for a certain period of time, typically one hour at about 180.degree. C., followed by reaction with lactide at about 200.degree. C. This process leads to block or graft copolymers which are useful due to their formation of a "hard" phase formed from the lactide repeating unit blocks, and a "soft" phase formed from the p-dioxanone repeating unit blocks (FIGS. 1, 2, 3 and 4).
Furthermore, U.S. Pat. No. 4,643,191 describes p-dioxanone-rich, poly(p-dioxanone-co-lactide) segmented copolymers comprising about 70 weight percent to about 98 weight percent polymerized p-dioxanone with the remaining small portion of the copolymer polymerized with lactide.
Although the above described copolymers yield materials with excellent properties such as high strength and stiffness and long BSR (Braking Strength Retention) profiles as found with the block copolymers, or good strength and shorter BSR (Breaking Strength Retention) profiles as found for the p-dioxanone-rich segmented copolymers, there is a need in this art for new copolymer compositions having characteristics not found for the block copolymers of U.S. Pat. No. 5,080,665 and the segmented copolymers of U.S. Pat. No. 4,643,191.
Accordingly, what is needed in this art are novel copolymer compositions which are elastomeric, useful as, for example, adhesion prevention film barriers and other rubber toughened, absorbable medical devices such as foams for tissue scaffolds and hemostatic barriers.